Method and device for manufacturing and filling thin-walled beverage containers

ABSTRACT

A method for manufacturing and filling beverage containers ( 12 ) having thin walls and/or at least partially unstable shapes under the influence of heat is described, in which the containers ( 12 ) are manufactured by blow molding of preforms ( 10 ), then filled with a hot liquid filling product ( 16 ), next pressurized by a compressed gas ( 18 ), and then sealed. The preforms ( 10 ) and the containers ( 12 ) molded therefrom are pressurized during blow molding at a blow molding temperature, which is essentially below 110° C.

This claims the benefit of German Patent Application DE 10 2009 011583.8, filed Mar. 6, 2009 and hereby incorporated by reference herein.

The present invention relates to a method and a device for manufacturingand filling beverage containers having thin walls and/or at leastpartially unstable shapes under the influence of heat.

BACKGROUND

In sterile bottling of beverages, it is known that the air present inthe head space of the beverage container may be displaced, e.g., byintroducing liquid nitrogen, as is known from EP 0 481 019 B1, forexample. Adding liquid nitrogen largely displaces the total atmosphericoxygen present in the container, thereby achieving better shelf life ofthe beverage.

In hot bottling of beverages in PET containers, the thermal stability ofthe material and the vacuum stability of the container also constitute achallenge, which is met through various measures. Because of the lowglass transition point of approximately 75° C., the thermal stability ofPET is not sufficient for filling temperatures of sensitive products,which are usually bottled in temperature ranges between 85° C. and 92°C. Therefore, the material must usually be thermally crystallized inprocessing in the stretch blow molding machine. This is implemented by ahigh temperature of the processed preforms (so-called preformtemperature) and heated blow molds (120° C. to 160° C.). However, thisresults in much higher energy consumption because in these methods,additional cooling of the container by compressed air is necessarybefore unmolding. Another disadvantage is the limited output performancedue to the required crystallization time in the mold.

Compensation for the volume shrinkage of the filling product due tocooling may be implemented by a relatively complex bottle design, suchas that known from WO 2006/062829 A2, for example. These bottles, whichare suitable for hot bottling containers, are much heavier in comparisonwith conventional designs for cold bottling containers, are more complexto manufacture, and thus are also much more expensive. However, in viewof the high cost of raw materials, which will continue to rise in thefuture, it is becoming increasingly less economical to achieve theadvantages of hot bottling by way of a higher bottle weight.Furthermore, bottles having vacuum equalizing surfaces are moredifficult to label and in some cases have a definitely reducedstackability.

For this reason, JP 06 263 190 A describes a method for hot filling ofthin-walled containers, in which the container stability after thecooling phase is to be ensured by introducing liquid nitrogen, becauseits expansion counteracts the shrinkage process due to the cooling ofthe container contents.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a process sequence forcontainer manufacturing and filling, which will ensure an improvedenergy-efficient method of providing filled beverage containers in themost reliable possible manner starting from a preform, to its blowmolding to form a beverage container and then to hot filling. Oneprimary focus of attention is to ensure the least possible deviation inshape from the blow-molded container contour as a result of thesubsequent filling and cooling of the container and of the fillingproduct in the container.

The present invention provides a method for manufacturing and fillingbeverage containers having thin walls and/or at least partially unstableshapes under the influence of heat, in particular PET bottles or similarcontainers having a low thermal stability, the containers beingmanufactured by blow molding of preforms, then filled with a hot liquidfilling product (16), next pressurized by a compressed gas (18) and thensealed, by exposing the preforms and the containers molded therefrom toa blow molding temperature essentially below 110° C. during blowmolding. It is advantageous in particular when the blow moldingtemperature is essentially below 100° C. In numerous experiments,temperatures in a range of 80° C. to 90° C. in blow molding have provento be practical in particular. After blow molding, the containers and inparticular the container bottoms are cooled before transporting thecontainers to the filling machine. The containers are cooled toapproximately a typical ambient temperature (approximately roomtemperature or below). In order for the bottles not to shrinkexcessively after cooling of the hot-filled liquid filling product, thecontainers are exposed to nitrogen after filling. Furthermore, care istaken to ensure that the blow molding temperature is below 110° C.,preferably between 60° C. and 95° C. and most preferably between 80° C.and 90° C.

In a preferred variant of the method according to the present invention,liquid temperature-regulating medium flows through the blow mold via aduct system. For this temperature-regulating medium, essentially watermay be used if the blow molding temperature is not above 100° C. Theblow mold is usually connected by hose lines to a central distributor atthe center of the blow molding machine. A network of bores through whichthe temperature-regulating medium flows passes through the blow mold.Each of the two blow molds (per blow molding station) has twoconnections for the forward flow and return flow of the medium.According to the present invention, this medium transfers heat to theblow mold in this large-area bore labyrinth in a temperature range below110° C. The bottom of the blow mold normally has separate connectionsfor a second circuit at a different temperature. The bottom temperatureis preferably less than 30° C., preferably less than 10° C., ifpossible.

A special advantage of the method according to the present invention isthat the method may be performed at temperatures below 100° C. usingwater as the temperature-regulating medium for the blow molding ratherthan oil at 130° C. to 140° C., as is customary in the known relatedart. In other words, it is advantageously possible to work with waterinstead of oil as the temperature-regulating medium.

A traditional so-called hot-fill method works with blow moldingtemperatures of approximately 130° C. and filling product temperaturesof approximately 90° C. The drawn PET is then pressed against the hotmold wall during the blow molding operation to remove stresses from thematerial, so that after the subsequent contact with the hot fillingproduct at a later time, the PET bottle is unable to shrink back intothe undrawn preform. Because of the material structure thereby formed,it is also possible to speak of low-stress PET.

In contrast with these methods known from the related art, the presentinvention allows only a maximum blow molding temperature of 110° C.,preferably of approximately 80° C. to 90° C. (at a filling producttemperature of also approximately 90° C.), so that inherent stressesremain in the drawn PET to allow better compensation for the subsequentpressurization with nitrogen.

It may also be advantageous to send the containers to the fillingoperation immediately after the blow molding operation without anintermediate buffer or interim storage. The purpose of this is primarilyto establish largely the same conditions (moisture uptake, cooling) forall bottles and/or containers. In other words, no buffer is used betweenthe blow molding machine and the filling machine, but instead eachbottle is transferred to the filling machine in the same time period.The bottles are preferably kept with the same spacing in thistemporarily stored conveyance system. The constant conveyance timebetween the blow molding machine and the filling machine could not beguaranteed when using a buffer.

The method according to the present invention has the particularadvantage that the bottle quality is kept at a very constant levelbecause the same extent of shrinkage and thus always constant fillinglevels are largely ensured. Furthermore, combining the steps ofcontainer molding and container filling structurally, in time and interms of process engineering, as is preferred but is not absolutelynecessary, has the advantage that all parameters important for asatisfactory procedure are much more easily kept constant and/or may beinfluenced more easily in the desired manner than is the case with thetraditional method.

The method according to the present invention is used for fillingbeverage containers having thin walls and/or at least partially unstableshapes under the influence of heat, e.g., of PET bottles or similarcontainers having a low thermal stability with a hot liquid fillingproduct, which is bottled in the containers, after which thesecontainers are pressurized by a compressed gas and then sealed.According to the present invention, the containers are sent to thefilling operation after a blow molding operation, so that thecontainers, which are still hot after the blow molding operation, may besent to the filling operation without any major delay, using aconveyance system in which the bottles are cooled, if necessary. Thecontainers are therefore blown, conveyed, and filled with the hot liquidwithin short distances, in particular through design and/or structuralintegration of a blow molding station with a downstream filling station.

According to one embodiment variant of the method according to thepresent invention, the containers are treated and drawn with the aid ofa liquid-cooled drawing rod during the blow molding operation. Thecontainers may optionally be treated and drawn with the aid of a drawingrod, which is gas cooled and/or through which gas flows during the blowmolding operation. It is preferable here for a liquid or gas outlet tobe provided essentially on an end face of the drawing rod facing thebottom of the container to be molded. Essentially the bottom of thecontainer is cooled in this way; the side walls should also be largelycooled but a cold bottom is more important.

The method may provide for gaseous or liquid nitrogen to be used as thecompressed gas for acting upon the filled containers. The nitrogenensures that no partial vacuum exists in the containers after cooling,so the relatively thin-walled and/or bendable containers are notdeformed by the vacuum in an undesirable manner.

The filling product is typically filled into the container at atemperature above 60° C., in particular at a temperature above 75° C.The method according to the present invention is suitable in particularfor filling temperatures of the liquid filling product betweenapproximately 80° C. and 95° C., in particular between approximately 85°C. and 92° C. The filling pressure of the compressed gas introducedafter filling the container with liquid filling product may beapproximately 2 bar or more, so that the internal pressure of the cooledcontainers is still greater than the ambient atmospheric pressure at afilling product temperature of less than 4° C., which corresponds tostorage of the bottle in a refrigerator.

Another goal of the present invention is to make available a device formanufacturing and filling containers, which is able to ensure animproved method of providing filled beverage containers in the mostenergy-efficient and reliable way possible from a preform by blowmolding to form a beverage container, which is then hot filled.

This goal is achieved with a device having the features of independentclaim 18. The present invention relates to a container processing devicefor molding and/or manufacturing beverage containers having thin wallsand/or at least partially unstable shapes under the influence of heat,e.g., PET bottles or such containers having a low thermal stability andalso for sterile filling thereof with a hot liquid filling product. Thecontainer processing device includes at least one container moldingstation for molding preforms to form beverage containers by a blowmolding method, a container filling station for filling the containerswith hot filling product, a gassing station for pressurizing the filledcontainers with a compressed gas, and a sealing device forpressure-tight and airtight sealing of the containers. According to thecontainer processing device according to the present invention, thecontainer molding station is formed by a blow molding station forstretch blow molding of the preforms to form plastic containers, theblow molding station including a blow mold having a duct system for atemperature-regulating medium to flow through, thetemperature-regulating medium being formed essentially by water. Theblow mold may be connected by hose lines, for example, to a centraldistributor at the center of the blow molding machine. A network ofbores, through which the temperature-regulating medium flows, passesthrough the blow mold. Each of the two blow molds usually present perblow molding station has two connections for forward flow and returnflow of the medium. In this large-area bore labyrinth, this mediumtransfers heat to the blow mold, namely in a temperature range of lessthan 110° C., preferably less than 100° C. The bottom normally hasseparate connections for another temperature-regulating medium circuitat another temperature. The bottom temperature may preferably be lessthan 30° C. when cold, more preferably less than 10° C. A particularadvantage of this embodiment is that with the device according to thepresent invention, it is possible to work with water as thetemperature-regulating medium for the blow molds at temperatures below100° C., whereas in the related art, only oil may be used as thetemperature-regulating medium at temperatures of 130° C. to 140° C.

According to one embodiment variant of the device according to thepresent invention, the container molding station and the containerfilling station are integrated in design and/or structure. With thedevice according to the present invention, the container molding stationis preferably formed by a blow molding station for stretch blow moldingof the preforms to form plastic containers, the container fillingstation, which is combined with it in space and/or design, beingconnected thereto.

In another embodiment variant of the container processing deviceaccording to the present invention, the blow molding station has aliquid-cooled or gas-cooled and/or gas-purged drawing rod, an opening tothe liquid or gas outlet being situated essentially on an end face ofthe drawing rod facing the bottom of the container to be molded.

The device according to the present invention may be designed inparticular as a rotary machine for continuous container molding andcontainer filling in one integrated process.

The present invention provides a method for hot bottling, which has beenimproved and developed further in essential aspects in comparison withthe known methods. Hot bottling still takes place in a typicaltemperature range, which should usually be between approximately 85° C.and 92° C. To compensate for the volume shrinkage occurring in coolingof the hot-filled liquid, the method operates with pressurization.Pressurization is currently achieved by adding nitrogen because innumerous experiments with PET bottles, such nitrogen pressurization hasproven to be particularly advantageous. The improved process technologyof hot filling with pressurization makes it possible to revise theprocess engineering to be employed in hot bottling in some aspects,thereby providing novel variants. The result is a novel method claim forstretch blow molding and filling technology. To compensate for ordiminish the reshrinkage effects occurring in the drawn PET at thefilling temperature, in the method according to the present invention,the container is stabilized by pressurization, not by thermalcrystallization of the bottle. This means that pressurization is alsoutilized for mechanical stabilization in addition to volumecompensation. This has the advantage that thermal crystallization of thematerial is no longer necessary and it is possible to work withconventional blow molding technology. The present invention relates tothe manufacture of containers, e.g., PET bottles, as well as theirfilling. The PET bottles are hot filled and pressurized, with the blowmolding temperature typically to be set between 10° C. and 110° C.,preferably 60° C. and 95° C., and most preferably between 80° C. and 90°C. A preferred temperature range is 80° C. to 90° C.

If working with a buffer for the blow-molded containers between the blowmolding station and the filling station, it may be advantageous todischarge such containers whose dwell time in the buffer is too longbecause if the dwell time is too long, too much internal stress in thePET is dissipated, but this is a disadvantage and should be avoided inthe present context in the interest of the least possible shrinkage ofthe filled bottles which are exposed to gas and are cooling.

Finally, it should be pointed out that through the structuralintegration of the individual container processing stations and throughthe method steps defined by the present invention, particularly goodsuitability for sterile bottling of beverages in these containers isachieved.

Additional features, goals and advantages of the present invention arederived from the following detailed description of a preferred specificembodiment of the present invention, which is given as a nonrestrictiveexample and refers to the accompanying drawings. The same componentshere have the same reference numerals in principle and will not bedescribed repeatedly in some cases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic flow chart to illustrate successive methodsteps in hot bottling of beverage in containers.

FIG. 2 shows a schematic sectional diagram of a PET container blowmolded using a drawing rod.

DETAILED DESCRIPTION

The schematic flow chart in FIG. 1 shows successive method steps inmolding preforms to form containers and the subsequent hot bottling ofbeverages in these containers. The method presented here allows sterilefilling of beverage containers and/or PET bottles having thin wallsand/or at least partially unstable shapes under the influence of heat.These PET bottles are filled with a hot liquid beverage, after which thebottles are pressurized by nitrogen as a compressed gas and then sealed.

In a first method step 51, preforms 10 are molded by a blow moldingoperation to form beverage containers 12, which are filled with a hotbeverage 16 in a subsequent method step S2 by a suitable filling device14. Containers 12, which are still hot after the blow molding operation,are cooled in a controlled manner and then sent to filling operation S2.Containers 12 are blown, conveyed, and filled with hot liquid 16 withinshort distances, in particular through design and/or structuralintegration of a blow molding station with a downstream filling station.It may be advantageous in this context to be sure that bottles 12 remainat the same spacing, which is advantageous for ensuring constant fillingand shrinkage conditions. The design and/or structural integration mayalso be referred to as “blocking” of the blow molding machine andfilling machine.

In a subsequent method step S3, the air in the upper area of container12 is displaced by filling with liquid or gaseous nitrogen, so that themechanical stability of container 12 may at the same time be ensuredafter cooling of liquid 16.

In a subsequent method step S4, container 12, which has been filled withhot liquid 16 and pressurized with liquid or pressurized liquefiedcompressed gas 18, is sealed with a sealing cover 20. After sealingcontainers 12, compressed gas 18 evaporates slowly, while the pressurein the bottle increases. Containers 12 filled in this way may be sent toa packaging and/or storage logistics after a cooling phase and interimstorage, if necessary.

Gaseous or liquid nitrogen (N₂) in particular may be used as compressedgas 18 in method step S3. Nitrogen ensures that there will be no partialvacuum in containers 12 after cooling, so that containers 12, which haverelatively thin walls and/or are soft enough to bend, do not deform inan unwanted manner due to partial vacuum. Containers 12 are typicallyfilled with the liquid filling product at a temperature above 75° C. Themethod described here is suitable for bottling the beverage at fillingtemperatures between approximately 85° C. and 92° C. in particular. Thefilling pressure of compressed gas 18 introduced after fillingcontainers 12 with liquid 16 may be approximately 2 bar or more, so thatthe internal pressure of cooled containers 12 is slightly above theambient atmospheric pressure.

Reference numeral 8 in FIG. 1 denotes a container processing device,which includes the processing modules required for implementing methodsteps S1 through S4 described above in a structurally integrated manner,which is characterized by the frame surrounding the processing modules.Container processing device 8 thus includes at least one containermolding station for molding preforms 10 to form beverage containers 12by a blow molding method (method step S1), a container filling stationhaving filling device 14 for filling containers 12 with hot liquid 16(method step S2), a gassing station for pressurizing filled containers12 with a compressed gas 18 (nitrogen; method step S3), and a sealingdevice for pressure-tight and airtight sealing of containers 12 usingsealing cover 20 (method step S4). According to the exemplary embodimentof the present invention described here, the container molding stationand the containing filling station are integrated by design and/orstructurally in the manner described here, so that containers 12 undergoa controlled cooling between the container processing stations. This hasthe particular advantage that containers 12 shrink in a preciselycontrollable manner, so that largely constant fill levels may bemaintained. In addition, hygienic advantages are achieved through thestructural integration of container processing device 8 because the riskof contaminants may be significantly reduced on the very short pathbetween container molding and filling.

The schematic longitudinal sectional view in FIG. 2 illustrates oneembodiment variant of container molding using a blow mold 22 and adrawing rod 24 movable along the direction of longitudinal extent ofpreform 10 or container 12. Multipart blow mold 22 has an essentiallyknown design having at least two shell-type halves and a bottom part 26clampable thereto and a head part 28, which secures preform 10 duringthe molding operation and also secures finished molded container 12. Asalready mentioned, with the container processing method according to thepresent invention, preforms 10 or containers 12 are treated, i.e., drawnduring the blow molding operation by liquid or gas and/or with drawingrod 24. Liquid or gas is allowed to escape essentially at one end face32 oriented to bottom 30 of drawing rod 24 facing container 12 to bemolded. Essentially only bottom 30 of container 12 is cooled in thisway, while side walls 34 may retain the high temperature prevailingduring the blow molding operation.

The present invention is not limited to the exemplary embodimentspresented above. Instead, a plurality of variants and modifications isconceivable, making use of the idea according to the present inventionand therefore also falling within the scope of the present invention.

LIST OF REFERENCE NUMERALS

-   8 Container processing device-   10 Preform-   12 Container-   14 Filling device-   16 Liquid, beverages-   18 Compressed gas-   20 Sealing cover-   22 Blow mold-   24 Drawing rod-   26 Bottom part-   28 Head part-   30 Bottom-   32 End face-   34 Side wall-   S1 First method step-   S2 Second method step-   S3 Third method step-   S4 Fourth method step

1. A method for manufacturing and filling beverage containers havingthin walls and/or at least partially unstable shapes under the influenceof heat, comprising: blow molding performs to form a container, theperforms and containers molded therefrom pressurized during blow moldingat a blow molding temperature below 110° C.; filling the container witha heated liquid filling product; pressurizing the filled container witha compressed gas; and sealing the filled and pressurized container. 2.The method as recited in claim 1 wherein the blow molding temperature isbelow 100° C.
 3. The method as recited in claim 2 wherein the blowmolding temperature is in a range of approximately 80° C. to 100° C. 4.The method as recited in claim 3 wherein the blow molding temperature isin a range of 80° C. to 90° C.
 5. The method as recited in claim 1wherein a blow mold has a liquid temperature-regulating medium flowingthrough the blow mold via a duct system.
 6. The method as recited inclaim 5 wherein the temperature-regulating medium is water.
 7. Themethod as recited in claim 1 wherein the containers, which are still hotafter the blow molding operation, are cooled on a conveyance path to thefilling operation.
 8. The method as recited in claim 1 wherein thecontainers are sent directly to the filling operation after blowmolding.
 9. The method as recited in claim 1 wherein at least someindividual containers are stored temporarily in a buffer storage atleast from time to time before filling and after blow molding.
 10. Themethod as recited in claim 1 wherein the containers are blown, conveyed,and filled with the hot liquid through design and/or structuralintegration of a blow molding station with a downstream filling station.11. The method as recited in claim 1 wherein the containers are treatedand drawn during the blow molding operation by a liquid-cooled and/orliquid-rinsed drawing rod or by a gas-cooled and/or gas-purged drawingrod.
 12. The method as recited in claim 11 wherein liquid or gas escapeson an end face of the drawing rod directed toward a bottom of thecontainer to be molded.
 13. The method as recited in claim 1 wherein thecompressed gas is nitrogen.
 14. The method as recited in claim 1 whereinthe liquid filling product is filled into the container at a temperatureabove 60° C.
 15. The method as recited in claim 14 wherein the liquidfilling product is filled into the container at a temperature above 75°C.
 16. The method as recited in claim 1 wherein the filling pressurewhen the compressed gas is introduced is more than 2 bar.
 17. The methodas recited in claim 1 wherein the containers are PET bottles orcontainers having a low thermal stability.
 18. A container processingdevice for molding and/or manufacturing beverage containers having thinwalls and/or at least partially unstable shapes under the influence ofheat and for sterile filling with a heated liquid filling product, thecontainer processing device comprising: a container molding station formolding preforms to form beverage containers by a blow molding method; acontainer filling station for filling the containers with a heatedliquid filling product; a gassing station for pressurizing the filledcontainers with a compressed gas; and a sealing device forpressure-tight and airtight sealing of the containers, the containermolding station being formed by a blow molding station for stretch blowmolding to form the plastic beverage containers, the blow moldingstation including a blowing mold having a duct system for atemperature-regulating medium to flow through, thetemperature-regulating medium being water.
 19. The device as recited inclaim 18 wherein the container molding station and the container fillingstation are spatially and/or structurally integrated or combined. 20.The device according to claim 18 wherein the blow molding station has aliquid- or gas-cooled drawing rod, an opening for the escape of liquidor gas being situated on an end face of the drawing rod facing a bottomof the container to be molded.
 21. The device as recited in claim 18wherein the device is a rotary machine for continuous container moldingand container bottling in an integrated process.